I started exporting a scene from TVPaint and was wondering why it seemed to be taking ages, so I opened Activity Monitor to see that TVPaint is only using 1.84 GB or RAM when there is 64 GB installed in the computer. I tried changing the cache settings in preferences from Auto to Manual but it hasn't made a difference, it's still only using 1.85 GB of RAM.

Cache has no connection with export : Cache is the extra memory that TVPaint uses to have a quick access to images, display, etc.... while you are using at it. It helps it to be used faster.

Now regarding export, I know the code has been improved to render images the fastest. However, even with a very powerful computer there is still an incompressible amount of time (even a few seconds) that is necessary. I will ask a developer to give you more details, I must admit it's a little beyond my knowledge

Export time depends on a lot of things and the amount of RAM used is not one of these.
It depends on the dimensions of your project, the length of your project, the format and options used to export and the power of your computer.

Can you give us these informations so we can help you to figure out what is slowing down your export ?

Project dimension: 2880 x 1620 pixels
Length: 123 frames
10 layers of scanned images (PNGs) with Basic scan cleaner used on them
Export settings: we are using a script someone on here recommended which exports all the layers of the project into folders and reimports them into After Effects with the same settings as the TVPaint file. It's saving us so much time as we don't have to export each layer individually to rebuild in After Effects (some scenes have 70 layers when they have colour and matte layers!) , but the only thing is that it doesn't give an option to set export settings, so that's the only downside.
Computer: Late 2013 Mac Pro with 64GB RAM, 3.5 GHz 6-Core processor, 64 bit version of TVPaint, OS X 10.9.5

It's just finished exporting, and it's taken nearly three hours to export 13 layers, whereas a previous export of the same scene with 85 total layers it took one hour. Both were exported to our server which is via the internet, so could that be a factor?